A communication system that includes a transmission device transmitting a packet and a reception device receiving the packet is known. In a communication system of this kind, when the amount of packets transmitted by the transmission device to the reception device per unit time (a communication load) becomes excessive, a delay time becomes excessive, or the packets do not reach the reception device (i.e., the packets are lost). A delay time is a time for a packet to reach the reception device from the transmission device.
The communication system described in Non-Patent Documents 1 and 2 estimate a mathematical model representing the behavior of a packet before reaching the reception device from the transmission device, and regulate the amount of packets transmitted by the transmission device (e.g., the bit rate of data that becomes the basis of a packet) based on the estimated mathematical model. Therefore, in the communication systems described above, the transmission device needs to acquire behavior information that represents the behavior of a packet and estimate a mathematical model based on the acquired behavior information.
In a communication system described in Non-Patent Document 3, every time receiving a packet, the reception device acquires a time when the packet is received (a reception time), and transmits the acquired reception time to the transmission device.
[Non-Patent Document 1] M. Kalman, B. Girod, “MODELING THE DELAYS OF SUCCESSIVELY-TRANSMITTED INTERNET PACKETS,” 2004 IEEE International Conference on Multimedia and Expo (ICME), IEEE-Press, June 2004, Vol. 3, pp. 2015-2018
[Non-Patent Document 2] Z. Liu and three others, “Traffic modeling with gamma mixtures and dynamical bandwidth provisioning,” Proceedings of the 4th Annual Communication Networks and Services Research Conference, IEEE-Press, 2006, pp. 123-130
[Non-Patent Document 3] T. Friedman and two others, “RTP Control Protocol Extended Reports (RTCP XR),” RFC3611, IETF (Internet Engineering Task Force) November 2003
Therefore, the transmission device can acquire behavior information that represents a delay time based on the reception time and based on a time when the transmission device transmits a packet (a transmission time). Consequently, the transmission device can estimate the abovementioned mathematical model based on the acquired behavior information. However, the communication system has a problem that a communication load becomes excessive because the reception device transmits behavior information for each packet to the transmission device. That is to say, there is a problem that a communication load when the transmission device acquires information representing the behavior of a plurality of packets becomes excessive.